Added a failing test for no results to DDBv2.
Solving bugs on empty results and between comparisions

When it returns empty result the result _results_left is true by
default and it tries to get data that doesn't exist.
When a between condition is added on the query the parameters needs to
be two separated string values ( not a SS field )
Updated tests to accommodate the changes to ``_build_filters``.
Merge branch 'ddb2-improvements' into develop